The present disclosure is generally directed to polyester synthesis processes and, more specifically, to processes for the synthesis of polyester resins which may be utilized in the formation of emulsion aggregation toners.
Electrophotographic printing utilizes toner particles which may be produced by a variety of processes. One such process includes an emulsion aggregation (“EA”) process that forms toner particles in which surfactants are used in forming a latex emulsion. See, for example, U.S. Pat. No. 6,120,967, the disclosure of which is hereby incorporated by reference in its entirety, as one example of such a process.
Combinations of amorphous and crystalline polyesters may be used in the EA process. This resin combination provides toners with high gloss and relatively low-melting point characteristics (sometimes referred to as low-melt, ultra low melt, or ULM), which allows for more energy efficient and faster printing. The choice of crystalline polymer may be important as poor crystalline-amorphous polymer combinations may result in toners that either do not show low-melt behavior or exhibit unacceptable heat cohesion properties.
Control of the distribution of the crystalline component within a polyester EA toner particle may be important in realizing optimal toner performance, especially in the area of charging, where crystalline polyesters on the particle surface can lead to poor charge (this may be caused, in some cases, due to the conductivity of the crystalline polyester resin). For example, EA ULM toners have been developed which use an amorphous polyester shell to limit the migration of crystalline polyester to the toner particle surface. The crystalline component may be sequestered in the interior of core-shell nanoparticles, surrounded by an amorphous resin shell. Molecule-level confinement may thus prevent the crystalline material from migrating to the toner particle surface, thereby providing desirable charging characteristics.
There is a continual need for improving polyester resins synthesis, as well as the use of polyesters in the formation of EA ULM toners.